本文選題：方波交流TIG-MIG + 電弧物理特性　； 參考：《山東大學(xué)》2017年碩士論文

【摘要】：TIG焊接過程穩(wěn)定,焊縫成形良好,但存在焊接效率低下的不足;傳統(tǒng)單MIG焊接具有生產(chǎn)效率高,且易于實(shí)現(xiàn)自動(dòng)化等優(yōu)點(diǎn),但焊接過程不夠穩(wěn)定。隨著現(xiàn)代工業(yè)的發(fā)展,傳統(tǒng)焊接工藝難以滿足人們對(duì)于高效低成本焊接的需求。因此,眾多高效焊接工藝出現(xiàn)并迅速發(fā)展。直流TIG-MIG復(fù)合焊接有效克服單獨(dú)焊接工藝不足,綜合焊接工藝的優(yōu)點(diǎn),在高效焊接領(lǐng)域得到廣泛認(rèn)同。但當(dāng)設(shè)置TIG焊接為小參數(shù)焊接電流時(shí),直流TIG-MIG復(fù)合焊接穩(wěn)定性差,斷弧現(xiàn)象嚴(yán)重,駝峰缺陷難以克服,并伴有嚴(yán)重的焊接飛濺。改變焊接工藝參數(shù),對(duì)TIG-MIG復(fù)合焊接工藝進(jìn)行優(yōu)化具有十分重要的意義。方波交流具有正半波與負(fù)半波轉(zhuǎn)換速度快,零點(diǎn)過渡區(qū)幾乎為零,電弧穩(wěn)定等優(yōu)點(diǎn)。本文提出在TIG焊接參數(shù)選擇上,利用方波交流代替直流進(jìn)行方波交流TIG-MIG復(fù)合焊接工藝試驗(yàn),為該工藝后續(xù)優(yōu)化及工程應(yīng)用提供理論基礎(chǔ)。從焊接過程斷弧數(shù)量、電參數(shù)波形等方面對(duì)比分析了直流TIG-MIG復(fù)合焊接工藝和方波交流復(fù)合焊接工藝焊接過程的穩(wěn)定性,結(jié)合焊縫成形,客觀分析兩種工藝的優(yōu)勢(shì)與不足。小參數(shù)TIG直流TIG-MIG復(fù)合焊接整體穩(wěn)定性差,斷弧現(xiàn)象嚴(yán)重,焊縫成形較差,駝峰現(xiàn)象難以克服,并伴有大量飛濺。方波交流TIG-MIG復(fù)合焊接斷弧較少,電參數(shù)波形更加穩(wěn)定,焊縫成形良好,極性比為10焊接工藝最優(yōu)。分析了方波交流TIG-MIG復(fù)合焊接電弧物理特性,并對(duì)極性比對(duì)該工藝電弧物理特性的影響展開研究。時(shí)間方面,極性比增大,復(fù)合電弧吸引時(shí)間增長(zhǎng),排斥時(shí)間縮短。電弧形態(tài)方面,極性比增大,復(fù)合電弧強(qiáng)度增強(qiáng),兩電弧電磁力作用強(qiáng)化,吸引和排斥形態(tài)更加明顯。極性比小,復(fù)合電弧形態(tài)收縮,電弧集中,熱量集中。分析了方波交流TIG-MIG復(fù)合焊接熔滴過渡特點(diǎn),并探究極性比對(duì)熔滴過渡的影響機(jī)理。當(dāng)TIG處于方波交流正半波時(shí),MIG焊絲尖端熔化液態(tài)金屬明.顯后偏,向熔池后方過渡;負(fù)半波時(shí),焊絲端部熔化液態(tài)金屬前偏向熔池前方過渡。方波交流TIG-MIG復(fù)合焊接工藝MIG過渡熔滴主要維持后偏的過渡形態(tài),過渡進(jìn)入熔池的后方。隨著極性比的增大,過渡熔滴向熔池后方過渡時(shí)間縮短,以前偏形態(tài)向熔池前方過渡時(shí)間增長(zhǎng)。分析了方波交流TIG-MIG復(fù)合焊接熔池流動(dòng)特點(diǎn)及駝峰缺陷機(jī)理,并對(duì)極性比對(duì)熔池流動(dòng)的影響展開研究。極性比為0(直流),MIG焊絲尖端錐狀液柱始終后偏過渡進(jìn)入熔池尾部。盡管由于液態(tài)金屬層較厚,其對(duì)后向液體流的驅(qū)動(dòng)作用較小,熔池液態(tài)金屬流向尾部形成壁面通道及熔池腫塊,容易形成駝峰。極性比為10,波形處于負(fù)半波時(shí),過渡熔滴進(jìn)入熔池的位置在一范圍內(nèi)變化,不會(huì)對(duì)熔池形成持續(xù)的后推力,熔池金屬的后向流速變小,不會(huì)在焊縫區(qū)域出現(xiàn)熔池腫塊現(xiàn)象。極性比為40,波形處于負(fù)半波時(shí),過渡熔滴前偏進(jìn)入熔池前部,熔滴撞擊弧坑前沿,后向液態(tài)金屬流以較大的速度向熔池尾部流動(dòng),在后方形成液態(tài)金屬凹陷,形成駝峰。
[Abstract]:The TIG welding process is stable, the weld forming is good, but the welding efficiency is low. The traditional single MIG welding has the advantages of high production efficiency and easy to realize automation, but the welding process is not stable. With the development of modern industry, the traditional welding technology is difficult to meet the people's demand for high efficiency and low cost welding. The direct current TIG-MIG composite welding has been widely recognized in the field of high efficiency welding. However, when TIG welding is a small parameter welding current, the stability of the DC TIG-MIG welding is poor, the arc breaking phenomenon is serious, and the hump defect is difficult to overcome. With serious welding spatter, it is of great significance to change the welding process parameters and optimize the TIG-MIG composite welding process. The square wave communication has the advantages of fast transition speed of positive half wave and negative half wave, almost zero transition zone in zero point, stable arc and so on. This paper proposes the use of square wave AC to replace DC in the selection of TIG welding parameters. The process test of square wave AC TIG-MIG composite welding is carried out to provide a theoretical basis for the subsequent optimization and engineering application of the process. The stability of the DC TIG-MIG composite welding process and the square wave AC composite welding process is compared and analyzed from the number of arc breaking and the waveform of electrical parameters. The objective analysis of two is to analyze the welding process of the square wave AC composite welding. The advantages and disadvantages of the technology are poor. The small parameter TIG DC TIG-MIG composite welding has poor overall stability, serious arc breaking phenomenon, poor weld formation, the hump phenomenon difficult to overcome, and a large amount of splash. The square wave AC TIG-MIG composite welding arc is less, the waveform of the electric parameters is more stable, the weld forming is good, the polarity ratio is the best welding process, and the analysis of the polarity ratio is the best. The arc physical characteristics of the square wave AC TIG-MIG composite welding are studied, and the influence of polarity ratio on the physical characteristics of the arc is studied. The time aspect, the increase of the polarity ratio, the increasing of the electric arc attraction time, the shortening of the rejection time, the increase of the arc shape, the increase of the polarity ratio, the intensification of the composite arc strength, the enhancement of the two arc electromagnetic force, the attraction and the absorption of the arc. The rejection morphology is more obvious. The polarity ratio is smaller, the compound arc shape contraction, the arc concentration, the heat concentration. The characteristics of the droplet transition in the Fang Bo AC TIG-MIG composite welding are analyzed and the influence mechanism of the polarity ratio on the droplet transition is explored. When the TIG is in the square wave alternating half wave, the MIG wire tip melts liquid metal clearly. During the negative half wave, the end of the welding wire is transferred to the front of the molten pool before the end of the welding wire is melted. The transition form of the transition droplet of the square wave AC TIG-MIG composite welding process mainly maintains the transition form after the transition, and the transition enters the rear of the molten pool. With the increase of the polarity ratio, the transition time of the transition droplet is shortened to the rear of the pool, and the former partial form is transferred to the front of the pool. The flow characteristics and hump defect mechanism of the square wave AC TIG-MIG composite weld pool are analyzed. The effect of polarity ratio on the flow of molten pool is studied. The polarity ratio is 0 (DC), and the tip of the MIG wire tip has always shifted to the rear of the molten pool. Although the liquid metal layer is thicker, its driving effect on the backward liquid flow When the liquid metal flows to the tail to form the wall channel and the pool mass, it is easy to form a hump. The polarity ratio is 10. When the wave is in the negative half wave, the position of the transition droplet into the pool is changed in one range, and the rear thrust of the molten pool will not be formed. The back flow velocity of the molten pool is smaller, and the weld pool mass will not appear in the weld zone. The polarity ratio is 40. When the waveform is in the negative half wave, the transition droplet goes into the front of the molten pool before the transition droplet, and the droplet hits the front of the arc pit. Then the liquid metal flow flows to the tail of the molten pool at a large speed, and the liquid metal sag is formed in the rear, and the hump is formed.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG456

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